Initially, he said that if he succeeds, he will "ding dong ditch" CNN founder Ted Turner's house while shooting his next movie in Atlanta. (In other words, he'll ring the doorbell and run, if he can even get close enough to the door of the mogul's estate.)

But over the past few days, Kutcher and others have upped the ante.

Prizes Galore for 1 Millionth Twitter Follower

On Tuesday night, the actor of Punk'd fame, and husband of actress Demi Moore, tweeted, "the 1 millionth person gets a guitar hero!" (Presumably referring to the popular video game.)

Later, he added that if he beat CNN to 1 million followers, he would buy 10,000 mosquito bed nets for World Malaria Day April 25.

Not to be outdone, a spokesperson for CNN told ABCNews.com that the company would match Kutcher's offer and will also buy the mosquito beds if it is the first to reach 1 million.

"Rather than trying to out-donate each other, we're trying to make sure that while it's a fun, engaging activity that some good can come out of it," she said.

But until this week, the CNN breaking news Twitter feed was not actually run by the cable news giant.

The spokeswoman confirmed that this week ownership was officially transferred to it from James Cox, a London technologist who started the CNN Twitter account in January 2007.

However, although CNN didn't previously outright own the Twitter account, the spokeswoman said it had been working alongside Cox for the past couple of years.

As for the Twitter race, she said it's a "healthy" challenge that is creating "socially responsible social media."

And ...They're Off!

Since Kutcher kicked off the "race" with a YouTube video Monday, he's upped his subscriber numbers from about 842,000 to more than 950,000. But the cable giant has also managed to boost its numbers from about 921,000 to 965,000.

According to the Twitter directory WeFollow, CNN's breaking news feed is still the most popular account on the micro-blogging site, but Kutcher has significantly narrowed the gap.

Kutcher: Number of Twitter Followers Is 'Crazy'

He's also overtaken Spears in the past few days. On Tuesday, she was No. 2 on the site but has now fallen behind Kutcher, with about 930,000 followers.

Kutcher started this Twitter race tizzy Monday when he posted a video to YouTube expressing his astonishment that he'd attracted hundreds of thousands of Twitter followers

"I just realized I have … 842,550 people that are following my Twitter feed, which is kind of scary to me now," he said. "Like I didn't realize that there were that many people following. That's kind of crazy."

Putting it in perspective for his fellow "citizens of the Inter Web," he added that CNN only had about 50,000 more followers than he does.

Amused by this distinction, he said, "If I beat CNN to 1 million followers I will literally go and ding dong ditch Ted Turner's house while I'm in Atlanta." (Kutcher will soon film "Five Killers" in the city, with Katherine Heigl and Tom Selleck.)

Before the actor signed off from his YouTube missive, he had some words for his acolytes: "To everyone who is following me on Twitter, you guys are awesome, and I just really enjoy the conversation we can have every day."

Fans, Phelps Join the Campaign

It didn't take long for his fans to respond with similar appreciation.

Soon after Kutcher posted his YouTube link to his Twitter feed, the Twittersphere was abuzz with his new challenge.

His followers started re-tweeting his post and asking others to join the campaign.

Even Olympian Michael Phelps has offered his support, encourging his 75,244 followers to help boost Kutcher's numbers. On Wednesday, he tweeted: "Guys, let's all help Ashton win the race to a million!"

One Millionth Follower Could Be in Video Game

Spotting an opportunity, video game published Entertainment Arts also decided to jump in and sweeten the pot.

On its own Twitter account, it wrote that Kutcher's one millionth follower will get a copy of every game the company makes in 2009 and would be featured in its upcoming game, The Sims 3.

And, Don Dodge, a Microsoft employee and tech blogger recently wrote that he thinks Kutcher might go down in Internet history as the first individual Twitter user to hit 1 million followers.

When he first wrote about celebs on Twitter in early April, Kutcher had 521,469 followers. But in just two weeks, he surpassed 753,000.

"He'll certainly be the first individual to reach a million followers. He may even beat CNN," Dodge told ABCNews.com.

He calculated that Kutcher is adding about 15,000 followers every day and expects him to have a million followers by April 21.